Complex Borides RERu₄B₄ (RE = Ce, Pr, Nd, Sm) - bonding peculiarities and magnetic properties

Trinath Mishra (1) , Matthias Eul (1) , Samir F. Matar (2) , Rainer Pöttgen (1)

1 Institut für Anorganische und Analytische Chemie
2 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

The rare earth borides RERu₄B₄ (RE = Ce, Pr, Nd, Sm) were synthesized from the elements by arc-melting and their crystal structures were studied on the basis of X-ray powder and single-crystal diffraction: LuRu₄B₄ type, I4₁/acd, a = 747.47(8), c = 1506.4(3) pm, wR₂ = 0.0579, 362 F² values for CeRu₄B₄, a = 751.3(2), c = 1507.1(5) pm, wR₂ = 0.0724, 471 F² values for PrRu₄B₄, a = 751.0(2), c = 1506.9(6) pm, wR₂ = 0.0598, 384 F² values for NdRu₄B₄, and a = 749.1(1), c = 1506.0(3) pm, wR₂ = 0.0759, 413 F² values for SmRu₄B₄, with 18 variables per refinement. Striking structural motifs of the RERu₄B₄ structures are Ru₄ tetrahedra and B₂ dumbbells with Ru-Ru and B-B distances of 271 and 180 pm in CeRu₄B₄. The intermediate valence of cerium leads to shorter Ce-Ru distances of 292 pm. CeRu₄B₄ behaves like a Pauli paramagnet with a small room temperature susceptibility of 1.5 × 10^-4 emu·mol^-1. Chemical bonding analyses shows substantial Ru-B and B-B bonding within the [Ru₄B₄] substructure.

Domaines: Matériaux

Trinath Mishra, Matthias Eul, Samir F. Matar, Rainer Pöttgen. Complex Borides RERu₄B₄ (RE = Ce, Pr, Nd, Sm) - bonding peculiarities and magnetic properties. Journal of Inorganic and General Chemistry / Zeitschrift für anorganische und allgemeine Chemie, 2010, 636 (7), pp.1236-1241. ⟨10.1002/zaac.200900562⟩. ⟨hal-00494477⟩